Oil stabilizing sequential hydrocracking and hydrogenation treatment

ABSTRACT

A process of improving the quality stability of hydrocracked oils by hydrogenating such oils subsequent to the hydrocracking treatment. The hydrocracking conditions comprise a temperature of from 700* to 900* F. and preferably from 700* to 800* F. and a pressure of at least about -500 psi and preferably at least about 1,500 psi over a sulfided mixture of Group VI B metal and Group VIII metal as a catalyst. The hydrogenation conditions comprise a temperature of from about 600* and preferably 625* to 675* F. a pressure of at least about 3,000 psi and the same catalysts as used for the hydrocracking operation.

United States Patent Thompson et al.

Kress; Albert T. Olenzak, both of Media, all of Pa.; lb Steinmetz,Wilmington, Del.

[73] Assignee: Sun Oil Company of Pennsylvania,

Philadelphia, Pa.

[22] Filed: Nov. 16, 1970 [21] App1.No.: 90,073

Related US. Application Data [63] Continuation-impart of Ser. No.694,096, Dec. 28,

1967, abandoned.

52 U.S.Cl ..208/58,208/18,208/97 [51] Int.Cl ..Cl0g37/06 5sFieldofSearch ..20s 15,1s,14,57,ss,59,

[56] References Cited UNITED STATES PATENTS 2,915,452 12/1959 Fear..208/57 [451 May 30, 1972 Primary Examiner-Herbert LevineAttorneyGeorge L. Church, Donald R. Johnson, Wilmer E. McCorquodale, Jr.and Frank C Hilberg, Jr.

[57] ABSTRACT A process of improving the quality stability ofhydrocracked oils by hydrogenating such oils subsequent to thehydrocracking treatment. The hydrocracking conditions comprise atemperature of from 700 to 900 F. and preferably from 700 to 800 F. anda pressure of at least about 500 psi and preferably at least about 1,500psi over a sulfided mixture of Group VI 8 metal and Group VIII metal asa catalyst, The hydrogenation conditions comprise a temperature of fromabout 600 and preferably 625 to 675 F. a pressure of at least about3,000 psi and the same catalysts as used for the hydrocrackingoperation.

7 Claims, No Drawings OIL STABILIZING SEQUENTIAL HYDROCRACKING ANDHYDROGENATION TREATMENT CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is a continuation-in-part of copending application Ser. No.694,096 filed Dec. 28, 1967, by Sheldon L. Thompson, Rene F. Kress,Albert T. Olenzak and lb Steinmetz and now abandoned.

BACKGROUND OF THE INVENTION In the past various processes have been usedfor upgrading lubricating oil stocks. These generally have involvedeither solvent extraction or hydrogenation including hydrocracking.Recently there has been an increasing demand for lubricating oils havingan increased viscosity index. Recent developments, and particularly inhydrocracking techniques has given birth to increased interest incommercial utilization of such techniques to upgrade lubricating oilsparticularly with respect to viscosity index. Briefly, this has involvedcatalytic hydrocracking of the lubricating oil stock at a temperatureabove about650 F. at high pressures. While such techniques have greatlyenhanced the viscosity index of the stocks so treated, they havesimultaneously caused said stocks to exhibit a marked increase in colordegradation on exposure to ultraviolet light and also to form greateramounts of sludge in the presence of oxygen during such exposure.

It is the main object of the present invention to substantially reducethe extent of color degradation in hydrocracked lubricating oils whichoccur upon exposure of such oils to actinic radiation and oxygen. It isa further object of this invention to reduce the sludge-formingcharacteristics of such lube oils under such conditions. Other objectsare to prepare lubricating oils in high yields, having a high viscosityindex, and of improved stability. It is still a further object toaccomplish each of the foregoing objects in an economical fashion.

SUMMARY OF THE INVENTION The present invention involves the discoverythat the stability of a hydrocracked lubricating oil can be improved byfurther hydrogenation using high pressure but at a temperature belowthat used in the hydrocracking step.

The hydrogenation of this invention may advantageously be used with anylube hydrocracking process which employs temperatures above about 700 F.together with high pressures. Such processes are described in U.S. Pat.Nos. 2,9l7,448; 2,960,458; 3,046,218; 3,078,221; 3,078,238; and3,088,908 the disclosures of which are hereby incorporated byreferences. A hydrocracking technique which is preferred for use in thepresent invention is described in U.S. Pat. No. 2,960,458 whichgenerally involves subjecting a deasphalted residuum having a viscosityindex between 75 and 100 and a viscosity at 210 F of between about 90and 200 S.U.S. to treatment with hydrogen at a temperature of from about735 to 825 F at a pressure above about 2,500 psi. up to 5,000 psi. oreven 10,000 psi. A pressure of 3,600 to about 4,000 psi is preferred. Aspace velocity of from 0.4 to L5 is generally used. The hydrocrackingreaction is carried out in the presence of a catalyst having botharomatic saturation and ring scission activity. Such catalysts are knownin the art. For instance they may comprise a sulfide of any metal ofGroup V! left-hand column of the periodic system mixed with a sulfide ofan iron group metal. Specifically the catalyst may be molybdenumsulfide, tungsten sulfide or chromium sulfide mixed with a sulfide ofiron cobalt and/or nickel. A particularly desirable catalyst is amixture of nickel sulfide and tungsten sulfide. Such a catalyst in aratio of 1 to 4 mols of nickel to 1 mol of tungsten (determined asmetals) has especially high activity and selectively. Other examples ofsatisfactory sulfide mixtures are cobalt sulfide-tungsten sulfide andnickel sulfidemolybdenum sulfide mixtures. The catalyst may be supportedor unsupported. A mol ratio of 1:1 of these mixtures has been foundsatisfactory. The product is subjected to dewaxing when necessary inorder to obtain yields of multi-grade oils of the desired viscosity itis essential to employ a residual type charge stock. The startingmaterial may be any residuum obtained by vacuum or like distillation ofany petroleum or residual fraction thereof which after deasphalting (ifnecessary), preferably with a low boiling hydrocarbon such as propane,propylene, or butane, has a viscosity index and a viscosity at 210 F. ofto 200 S.U.S. Thus for instance, the resdiuum may be prepared by vacuumdistillation of a Pennsylvania, Mid-Continent, West Texas, Kuwait,Ordovician, Lagomedio, etc. crude. It has been found that deasphaltingwith agents such as sulfuric acid, phenol, sulfur dioxide, etc. resultsin removal of components which upon hydrogenation have desirableproperties for a multigrade oil product; and if these materials areemployed for asphalt removal, the product produced will not be of asgood quality, and the yield of multigrade oils will be lower. A highcarbon residue will result in undesirable shortening of the life of thecatalyst under the relatively sever hydrogen treatment conditionsemployed to produce the multi-grade oil. For this reason, it is usuallypreferred to employ charge stocks having a low carbon residue such asbelow about 2 (Conradson). However, higher carbon residue charge stockmay be used if catalyst life is not of great importance or a ruggedcatalyst is used. The utilization of a charge stock having a viscosityindex of 75 to is essential in obtaining a reasonable yield of a highviscosity index product i.e., a product having a viscosity index of overabout 100 is produced in good yield only if a charge stock having aviscosity index of at least about 75 is employed. A charge stockviscosity of between about 90 and 200 S.U.S. at 210 F. is necessary sothat the multi-grade oil product will have the proper viscosity afterthe hydrogen treatment.

The hydrogenation step which follows the above-described hydrocrackingstep serves to accomplish the desired results of reduced qualitydegradation as to both sludge and color. In this hydrogenation step ithas been found that not only is the temperature important but that theemployment of high pressure is particularly important. It has been foundthat sludge formation and quality stability in general is greatlyincreased by hydrogenating the hydrocracked lube stock at a temperaturein the range of about 600 and preferably 625 to 675 F. and a pressure ofat least about 3,000 psi.

Thepressure generally is in the range of 3,000 to 5,000 psi. Highlysatisfactory results are obtained at from 3,000 to 3,500 psi. Thepressures as used herein are the partial pressure of hydrogen. Thehydrogen employed can be a refinery stream as long as it does notcontain a significant'amount of a catalyst poisioning component. Thereis no theoretical upper limit on pressure, however, it is contemplatedthat the pressure'normally will not exceed about 10,000 psi. The partialpressure of hydrogen is important with respect to the hydrogenationaspect itself, however, total pressure is important with respect to themaximum temperature to be employed. Since cracking is to be essentiallyavoided, the temperature normally cannot exceed about 675 F, however,this limit has some upward flexibility if high enough pressures areemployed to substantially prevent any cracking. Because the effect ofincreasing pressure is to increase the capital and operating cost, thepressure will preferably be kept at the minimum required to accomplishthe desired results. The temperature should be kept in the range ofabout 600 to 675 F as indicated above in spite of pressure adjustmentsmaking higher temperatures possible because from an overallconsideration such temperatures are No. 1,024,317 issued to that companyon Mar. 30, 1966. Examples of other supports for such catalyst areactivated.

The residence time expressed as liquid hourly space velocity(L.1-l.S.V.) will generally fall in the range of about 0.1 to 1.0. Bestresults are generally when the L.H.S.V. is about 0.5 volume of liquidfeed per volume of catalyst.

The hydrogen recycle in the hydrocracking step generally is 2,500 to10,000 S.C.F. per barrel of charge. In contrast to the hydrocrackingstep little or no hydrogen recycle is required in the hydrogenation stepunless desired for quenching to control temperature. The hydrogenconsumption in the hydrogenation step normally is in the range of from150 to 200 S.C.F. of hydrogen per barrel of charge stock.

DESCRlPTION OF THE PREFERRED EMBODIMENTS Hydrocracking RefiningProcedure A charge stock of Grade B solvent lube crude mix was chargedto a crude still and fractionated into approximately 70 percent and 30percent of overhead and bottoms, respectively. The bottoms had an intialboiling point of 650 F. at atmospheric pressure. The bottoms werecharged to a vacuum still and fractionated to produce a gas oil, adistillate stock and a residual asphalt stock; the latter two hadinitial boiling points of about 695 and 750 F respectively. The residualstock was deasphalted and extracted by the Duo-Sol process (i.e., whichemploys propane and a mixture of phenol-cresol as solvents) atapproximately 130 F. The raft'mate from the deasphalter and thedistillate stock from the vacuum still when combined had the followingproperties:

HYDRO CRACKER OHARGE PROPERTIES Gravity, AP1, Vacuum distillation rangeat 2 mm. adjusted to 760 mm. 30.5

int. 694 5% 760 784 30% 829 50% 881 70% 964 E.P. 1030 Recovery,% 83Aniline Pt. 239.2 SSU/210 59.7 Avg. M.W. 505 Wt. Aromatics 22.4

The foregoing mixture was charged to a hydrocracker and said materialwas hydrocracked in the manner described in Us. Pat. No. 2,960,458. Ahydrogen stream comprising gas and hydrogen, of which about 85 per centwas hydrogen, was used in the hydrocracking reaction.

The crude hydrocracked product was charged to a stripper or atmosphericstill and fractionated to produce gas, naphtha and fuel oil and a waxylube of initial boiling point of approximately 700 F. At this point, aproduct of about 105 viscosity index was obtained on a dewaxed basis.The quality stability is reported below.

Stabilizing Hydrogenation The foregoing hydrocracked lube fraction wascharged to conventional high pressure hydrogenation equipment containingone bed of catalyst and it was hydrogenated therein. The catalyst andreaction conditions are set forth in Table I below. Product from thehydrogenation was charged to a dewaxer and dewaxed to a pour point ofapproximately 0 F. The product quality as to color, color stability andsludge formation of the hydrocracked product and the combinationhydrocracked and mildly hydrogenated product are set forth also in Tablel for comparison purposes.

TABLE 1 Hydrocracked Hydrocracked Oil Hydrofinished HydrogenationCatalyst NiMo Hydrogen Partial Pressure, 3000 p.s.i.g. Temperature, F.-625 L.H.S.V. 0.5 initial D1500 1.5 1.5 D1500 Color after 45 hrs. 5.0[.75 exposure to UV. light Heavy Nil Sludge Stability Test Procedure Thestability test procedure employed was as follows: A 30 ml. sample of thematerial to be tested was placed in a ml. beaker. Two 275 wattultraviolet sunlamps were placed approximately 12 inches away from thesurface of the sample. The sample was placed in an air ventilated ovenon a rotating table and heated to F The ultraviolet light was turned onwhen the sample was placed in the oven. After 45 hours, color of thetest samples were determined using the ASTM-Dl 500 test. The sludgeformed was determined qualitatively by visual observation.

For comparison purposes, tests were made on typical commercial fractionsof commercial product, hydrocracked product and also the product of thecombination of hydrocracking followed by mild hydrogenation (with thenickel-molybdenum catalyst) in accordance with the present invention.The products of each method were fractionated into both typical andcomparative commercial fractions. The results of the color and sludgetests are reported in Table II as follows:

TABLE II [Comparison of UV stability of commercial product,liydrocracked product with and without mild hydrogenation] Typical'Hydrocracked commercial Hydrocracked and hydroproduct oils I o finishedoils Fraction #1 #2 #4 #1 #2 #4 #1 #2 #4 D1500 color,

initial 0. 5 l. 0 1. 75 0. 75 1. 25 2. 25 0. 25 0. 75 1. 25 D1500 color,after 45 hrs. exposure to UV light-.. 4. 5 4. 0 4. 5 5. 75 5. 75 5. 0 1.00 1. 25 2. 0 D1500 color 4. 0 3. 0 2. 75 5.0 4. 5 2. 75 0.75 0. 50 0.75Sludge Nil Nil 1 Heavy.

2 Medium.

3 Light.

4 Haze.

Similar results have been obtained when the product was carried out in asingle reactor with two beds of the same catalyst, namely,nickel-tungsten sulfides. The temperature of the top bed wasapproximately 760 F. where hydrocracking occured and the temperature ofthe bottom bed as approxicatalyst bed. The hydrogen partial pressure wasmaintained at 3,000 psi in both beds.

We claim:

1. A process of improving the viscosity index and quality stability oflube oils which comprises first hydrocracking a lube oil fraction over asulfided mixture of an iron group metal and a metal of Group VI lefthand column of the periodic system at a temperature of about from 735 to825F. at a hydrogen partial pressure above about 2,500 psi. to produce ahydrocracked lube oil fraction, and then hydrogenating said hydrocrackedlube oil fraction over a sulfided mixture of an iron group metal and ametal of Group VI left hand column of the periodic system at atemperature of from 600 to 675 F. and a hydrogen partial pressure of atleast 3,000 p.s.i.

2. The process of claim 1 wherein the hydrogenation step is carried outat from about 625 to 675 F.

3. The process of claim 2 wherein the hydrocracking catalyst compositionis a nickel sulfide-tungsten sulfide com- 5 bination.

4. The process of claim 3 wherein the hydrogenation catalyst is a nickelsulfide-molybdenum sulfide combination.

5. The process of claim 4 wherein the hydrogenation catalyst is a nickelsulfide-tungsten sulfide combination.

6. The process of claim 4 wherein the liquid hourly space velocity inthe hydrogenation step is about 0.5.

7. The process of claim 5 wherein the liquid hourly space velocity inthe hydrogenating step is about 0.5.

- IF i

2. The process of claim 1 wherein the hydrogenation step is carried outat from about 625* to 675* F.
 3. The process of claim 2 wherein thehydrocracking catalyst composition is a nickel sulfide-tungsten sulfidecombination.
 4. The process of claim 3 wherein the hydrogenationcatalyst is a nickel sulfide-molybdenum sulfide combination.
 5. Theprocess of claim 4 wherein the hydrogenation catalyst is a nickelsulfide-tungsten sulfide combination.
 6. The process of claim 4 whereinthe liquid hourly space velocity in the hydrogenation step is about 0.5.7. The process of claim 5 wherein the liquid hourly space velocity inthe hydrogenating step is about 0.5.